The present invention relates generally to planar optical systems and more particularly to planar optical systems utilizing geodesic lens elements.
Recent developments in the integrated optics field have resulted in the design and development of integrated optic spectrum analyzers, and the like. A typical spectrum analyzer device is described in a publication by M. K. Barnoski et al entitled "Design, Fabrication and Integration of Components for an Integrated Optic Spectrum Analyzer", 1978 Ultrasonic Symposium Proceedings, IEEE, pages 74-78. The basic integrated optic spectrum analyzer comprises a laser source which transmits light along a planar waveguide layer deposited on the surface of a substrate. Geodesic lenses are disposed in the substrate and the waveguide layer conforms to the contour of the substrate. For example, a geodesic lens collimates laser light through a surface acoustic wave device which deflects the collimated laser beam in proportion to the strength or frequency of the signals applied to the surface acoustic wave device. After the laser light passes through the surface acoustic wave device, a second geodesic lens refocusses the light onto a photoelectric detector array.
Heretofore, in order to insure that the laser source and detector array were precisely located at the focal planes of the geodesic lenses, it was necessary to remove excess material from the ends of the substrate and waveguide layer prior to locating the laser source and detector elements. The shortcomings of this approach are that it cannot correct for lenses with focal lengths in excess of the platelet dimension; that is, where substrates and waveguide layers are shorter than the focal length of the geodesic lenses. Fabrication of the geodesic lens system, therefore, is only a one-way method. The platelet may be shortened to properly place the laser source or detector array at a focal plane of the geodesic lens located on the structure. Shortening of the platelet changes the over-all dimensions of the spectrum analyzer in an uncontrollable manner leading to assembly and installation problems.
Therefore, it would be an improvement in the integrated optics art to provide a means by which to adjust the positions of focal planes of lenses utilized in a geodesic lens system, or the like, without changing the dimensions of the structure.
It would also be an improvement in the integrated optics art to provide a means by which to correct for optical aberrations in a planar waveguide system which defocus light rays transmitted by the system.